[Phylogenetic analysis based on hemagglutinin and neuraminidase genes between swine influenza virus and human influenza A/H3N2 virus strains isolated in Zhejiang province].

Objectives: To investigate the phylogenetic relationship between swine influenza A/H3N2 virus and the representative strains of human influenza A/H3N2 virus isolated in two epidemics in recent years through comparing the sequences within HA and NA genes.

Methods: HA and NA gene of the human representative strains were sequenced, and then phylogenetic tree with the swine and human strains isolated in the corresponding period of time were constructed.

Results: The homologies on the HA1 domain between human representative strains (A/Zhejiang/10/98, A/Zhejiang/6/99 and A/Zhejiang/8/02)and the swine strains (A/SW/Ontario/130/97, A/SW/Hongkong/4361/99 and A/SW/Hongkong/74/02) were 99.1%, 99.4% and 99.4% respectively. Based on the NA gene, the homologies between human strains (A/Zhejiang/10/98, _A/Zhejiang/6/99 and A/Zhejiang/8/02)and the swine strains (A/SW/Ontario/130/97, A/SW/Hongkong/4361/99 and A/SW/Hongkong/74/02) were 98.2%, 99.3% and 99.3% respectively. The results showed that the two types of influenza viruses were highly homologue, and even some of their homologies were higher than that amongst the contemporary human influenza A/H3N2 strains. The same results shown in the phylogenetic tree.

Conclusions: The human influenza A/H3N2 virus isolates in the two epidemic closely associated with some of the swine influenza virus strains, and their relationship should be further studied.